The present invention relates to a Micromirror Array Lens device. Particularly, the present invention related to Micromirror Array Lens device reducing chromatic aberration for a light with broadband wavelength range.
There are two conditions to make a perfect lens. The first is the converging condition that all light rays scattered by one point of an object should converge into one point of an image plane. The second is the same phase condition that all converging light rays should have the same phase at the image plane. The surface shape of conventional reflective lens is formed to satisfy these perfect lens conditions by having all light rays scattered by one point of an object converged into one point of the image plane and the optical path length of all converging light rays to be the same.
The Micromirror Array Lens can simulate the perfect lens conditions by rotating micromirrors to make all light rays scattered by one point of an object converged into one point of an image plane and translating each micromirror to make all converging light rays to have the same phase. Even though the optical path length of converging light rays in the micromirror array is different from that of the equivalent conventional reflective lens, the same phase condition can be satisfied by adjusting the translational motion of each micromirror because the phase of light is periodic. The surface profile of Micromirror Array Lens using the same phase condition has a discontinuous surface profile.
The general principle and methods for making the Micromirror Array Lens are disclosed in U.S. Pat. No. 6,970,284 issued Nov. 29, 2005 to Kim, U.S. Pat. No. 7,031,046 issued Apr. 18, 2006 to Kim, U.S. Pat. No. 6,934,072 issued Aug. 23, 2005 to Kim, U.S. Pat. No. 6,934,073 issued Aug. 23, 2005 to Kim, U.S. Pat. No. 7,161,729 issued Jan. 09, 2007, U.S. Pat. No. 6,999,226 issued Feb. 14, 2006 to Kim, U.S. Pat. No. 7,095,548 issued Aug. 22, 2006 to Cho, U.S. patent application Ser. No. 10/893,039 filed Jul. 16, 2004, U.S. patent application Ser. No. 10/983,353 filed Nov. 8, 2004, U.S. patent application Ser. No. 11/076,616 filed Mar. 10, 2005 and U.S. patent application Ser. No. 11/426,565 filed Jun. 26, 2006, all of which are incorporated herein by references.
The phase matching condition is only satisfied for monochromatic light. In general, light has a broadband wavelength range. In this case, when the phase matching condition is satisfied for one wavelength by the translational motion of the micromirror, the phase matching condition for other wavelengths can not be satisfied. The chromatic aberration is increased as the number of profile discontinuity of Micromirror Array Lens is increased. If micromirror array makes continuous reflective lens profile, there is no chromatic aberration. But, it is impractical because micromirrors should have huge translation to make continuous reflective lens profile.
When the Micromirror Array Lens is required to have small optical power, chromatic aberration caused by the profile discontinuity is small. However, when the Micromirror Array Lens is required to have large optical power, the number of profile discontinuity is increased. In this case, the chromatic aberration is increased.
To reduce profile discontinuity and chromatic aberration, Hybrid Micromirror Array Lens is introduced in this application.